Question

Which one of the following species doesn't have a magnetic moment of $1.73 \,B M$, (spin only value)?

• A. $O _{2}^{+}$
• B. $CuI$
• C. $\left[ Cu \left( NH _{3}\right)_{4}\right] Cl _{2}$
• D. $O_{2}^{-}$

Answer 1

Answer: (B)

Species must not contain single unpaired
(1) $O_{2}^{+} \rightarrow \sigma_{1 s}^{2} < \sigma_{1 s}{ }^{* 2} < \sigma_{2 s}{ }^{2}< \sigma_{2 s}{ }^{* 2} < \sigma_{2 p}{ }^{2} < \pi_{2 p x}{ }^{2}=\pi_{2 p y}{ }^{2} < \pi_{2 p x}{ }^{*}=\pi_{2 p y}{ }^{*}$
unpaired $e^{-}=1 \therefore \mu=1.73 \,B M$
(1) $Cu ^{+} I^{-} Cu ^{+} \rightarrow[ Ar ] 3 d^{10} $
$\therefore $ unpaired $e^{-}=0$
$I^{-} \rightarrow[X e]$
$ \therefore $ unpaired $e^{-}=0$
therefore $\mu=0$
3. $\left[ Cu \left( NH _{3}\right)_{4}\right] Cl _{2}$
$C u \rightarrow[A] 3 d^{3} $
$\therefore $ unpaired $=1$
$ \therefore \mu=1.73 \,B M$
4. $O _{2}^{-} \rightarrow d$
$\sigma_{1 s}^{2} < \sigma_{1 s}{ }^{* 2} < \sigma_{2 s}{ }^{2} < \sigma_{2 s}{ }^{* 2} < \sigma_{2 p x}{ }^{2} < \pi_{2 p x}{ }^{2}=\pi_{2 p y}{ }^{2} < \pi_{2 p x}{ }^{*}=\pi_{2 p y}{ }^{*}$
$\left(11 e^{-}\right)$
$\therefore $ unpaired $\therefore \mu=1.73\, B M$